PCB Bypass Circuit for Polyphase Motor Noise Suppression
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Solution Overview
Problem
Existing printed circuit boards for polyphase motors face challenges in suppressing radiated noise due to power source voltage fluctuations, particularly when using high-speed switching elements like power MOSFETs, as the capacitors used to mitigate noise are often too far from the power converting units, leading to high wiring impedance and delayed power supply.
Innovation Solution
A printed circuit board design featuring a bypass circuit that connects two positive wires close to the power input terminals of the driving IC, along with capacitors strategically placed between these wires and the negative trunk line, effectively distributes inductive energy and reduces source voltage fluctuations, thereby suppressing radiated noise and ensuring efficient power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitors are disposed close to the power converting unit, then power supply impedance is lowered and source voltage fluctuation is suppressed, but the distance from the capacitor to the power converting unit becomes too long in polyphase motor circuits, causing high wiring impedance and delayed power supply
Solution Approach 1:
The patent divides the power supply path into multiple independent positive wires (first positive wire, second positive wire, etc.) that connect different power converting units directly to the power input terminal. This segmentation allows each capacitor to be connected to its corresponding switching circuit through a short, dedicated wire, reducing wiring impedance and preventing delayed power supply while maintaining noise suppression effectiveness.
Solution Approach 2:
The bypass circuit acts as an intermediary that connects the first positive wire with the second positive wire, enabling capacitors to share power supply paths while maintaining low impedance. This intermediary structure allows capacitors to be positioned optimally for noise suppression without creating excessively long wiring paths to individual power converting units.
2Speed
If high-speed switching elements like power MOSFETs are used, then motor response speed is improved, but power source voltage fluctuates with high frequency causing radiated noise
Solution Approach 1:
Capacitors are connected in parallel between positive lines and negative lines at strategic positions before the power converting units. These capacitors act as preliminary energy reservoirs that supply high-frequency current during switching operations, preventing voltage fluctuations and radiated noise while allowing high-speed switching elements to operate at full speed.
Solution Approach 2:
The patent changes the electrical parameters of the power supply system by introducing multiple capacitors with specific capacitance values connected through low-impedance paths. This parameter modification allows the system to handle high-frequency voltage fluctuations generated by fast switching elements, maintaining both high motor response speed and low radiated noise.
3Device complexity
If a single positive wire passes through multiple switching circuits, then wiring complexity is reduced, but wiring impedance becomes too high causing insufficient noise reduction effect
Solution Approach 1:
Instead of using a single positive wire that passes through multiple switching circuits, the patent segments the power supply into multiple independent positive wires. Each wire connects the power input terminal to a specific power converting unit with its own capacitor, reducing the total impedance of each power path while maintaining simple overall wiring structure through systematic arrangement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses radiated noise and ensures stable power supply to the motor by balancing energy distribution between capacitors, allowing for smooth operation and reduced noise interference, even at high-speed switching frequencies.
Implementation Method 1
a bypass circuit connecting the first positive wire with the second positive wire
Implementation Method 2
a first capacitor provided between the first positive wire and the negative trunk line, a second capacitor provided between the second positive wire and the negative trunk line
Data Source
AI summary
A printed circuit board includes a power input terminal, a positive trunk line, a negative trunk line, a first switching circuit, a second switching circuit, a first positive wire, a second positive wire, a first capacitor, a second capacitor, and a bypass circuit. The first positive wire connecting the positive trunk line with the first switching circuit without passing through the second switching circuit. The second positive wire connecting the positive trunk line with the second switching circuit without passing through the first switching circuit. The first capacitor provided between the first positive wire and the negative trunk line. The second capacitor provided between the second positive wire and the negative trunk line. The bypass circuit connecting the first positive wire with the second positive wire.